Answer:
(a) The self inductance, L = 21.95 mH
(b) The energy stored, E = 4.84 J
(c) the time, t = 0.154 s
Explanation:
(a) Self inductance is calculated as;

where;
N is the number of turns = 1000 loops
μ is the permeability of free space = 4π x 10⁻⁷ H/m
l is the length of the inductor, = 45 cm = 0.45 m
A is the area of the inductor (given diameter = 10 cm = 0.1 m)

(b) The energy stored in the inductor when 21 A current ;

(c) time it can be turned off if the induced emf cannot exceed 3.0 V;

Answer:
Explanation:
The trick is in finding the volume.
Final Volume = 26.64
Initial Volume=<u>20.92</u> Subtract
Metal Volume 5.72 cm^3
Density = mass / volume
Density = 72.17 / 5.72
Density = 12.617
Density applies to many if not all aspects of life. With density you can explain why ice floats. You can explain why oxygen is on the earth, and not floating around in space( or being replaced by another gas). You can also explain why heat rises while cold air sinks.
= 3.456 × 1011
(scientific notation)
= 3.456e11
(scientific e notation)
= 345.6 × 109
(engineering notation)
(billion; prefix giga- (G))
= 345600000000
(real number)
A land form or land mass to be created over a long period of time